Docs: Updated Title chunker references (#14483)

### What problem does this PR solve?

Updated Title chunker references

### Type of change

- [x] Documentation Update

docs/administrator/migration/database_schema_and_migration.md

@@ -0,0 +1,56 @@
+---
+sidebar_position: 1
+slug: /database_schema_and_migration
+sidebar_custom_props: {
+  categoryIcon: LucideLocateFixed
+}
+---
+
+# Database schema and migration
+
+Sync schemas and migrate data using official RAGFlow scripts.
+
+---
+
+RAGFlow handles schema updates and migrations automatically at startup. However, for high-volume environments like Kubernetes, massive datasets can cause initialization to exceed 10 minutes, potentially triggering container timeouts or health check failures. To avoid this, you can disable the built-in auto-initialization and manually run these provided scripts to complete database upgrades before launching the service:
+
+- [mysql_migration.py](#mysql_migrationpy): Migrates data between MySQL tables.
+- [db_schema_sync.py](#db_schema_syncpy): Syncs database schemas and manages changes using peewee-migrate.
+
+## mysql_migration.py
+
+The [mysql_migration.py](https://github.com/infiniflow/ragflow/blob/main/tools/scripts/mysql_migration.py) script is a specialized tool for re-organizing RAGFlow’s model-related data. It transitions data from older unified tables into a modern, multi-table structure to support advanced model management.
+
+### Key functions
+
+- **Sequential migration**: Moves data through three distinct stages—Provider, Instance, and Model—to maintain database integrity and satisfy dependencies.
+- **Flexible setup**: Connects to MySQL using either a YAML configuration file or direct command-line arguments.
+- **Execution control**: Offers three specific modes: dry-run (preview), table-only (structural setup), and execute (full data move).
+- **Automated mapping**: Generates unique IDs and handles complex joins between legacy records and new table structures.
+- **Batch logging**: Processes records in sets of 100 and provides a final summary of total duration and row counts.
+
+### When to use
+
+- **Version upgrades**: Essential when moving to RAGFlow v0.25 or later to ensure your models are correctly categorized in the new schema.
+- **Data normalization**: Necessary when consolidating multiple API keys or LLM providers into the updated system format.
+- **Kubernetes deployments**: Useful for setting up the database structure independently using the `--create-table-only` flag before main services start.
+- **Migration verification**: Used in dry-run mode to identify any legacy records that still need to be moved to the new tables.
+
+## db_schema_sync.py
+
+The [db_schema_sync.py](https://github.com/infiniflow/ragflow/blob/main/tools/scripts/db_schema_sync.py) script is a synchronization utility that ensures your MySQL database structure matches the Peewee ORM models defined in the RAGFlow source code.
+
+### Key functions
+
+- **Change detection**: Compares Python model definitions in `api/db/db_models.py` against the live database to identify new tables, added fields, or type mismatches.
+- **Migration generation**: Automatically creates Python migration files (containing `migrate()` and `rollback()` logic) in version-specific directories (e.g., `tools/migrate/v0_25_0/`).
+- **Schema auditing**: Provides a `--diff` command to view structural discrepancies without applying changes.
+- **Execution management**: Applies pending migrations to the database to bring it up to date with the current software version.
+- **Safety controls**: Prevents accidental data loss by requiring an explicit `--drop` flag to generate `DROP COLUMN` statements for removed fields.
+
+### When to use
+
+- **Version upgrades**: When moving to a new version of RAGFlow that introduces structural database changes.
+- **Development**: When modifying `db_models.py` and needing to update your local database without manual SQL.
+- **CI/CD pipelines**: To automatically prepare or apply database updates during deployment.
+- **Troubleshooting**: When the application fails due to "Unknown column" or "Table not found" errors, indicating a desynchronized schema.

docs/guides/agent/agent_component_reference/chunker_title.md

@@ -23,7 +23,30 @@ Placing a **Title chunker** after a **Token chunker** is invalid and will cause
 
 ## Configurations
 
-### Hierarchy
+### Hierarchy or Group
+
+Select how a document is split:
+
+- Hierarchy: Construct a heading tree and produce self-contained chunks, each carrying its full ancestral path (e.g. Part 1 › Chapter 3 › Section 2 + body text). Best for highly structured texts — such as legal statutes, regulations, contracts, and technical specs — where each chunk must be identifiable by its position in the hierarchy.
+- Group: Split the document flat at a chosen heading level, merging adjacent small sections to ensure semantic flow. Chunks exclude ancestral path. Best for documents with flowing, contextually connected content — such as books, manuals, reports, and articles — where narrative coherence depends on keeping adjacent paragraphs together.
+
+#### Separate parent-heading content
+
+:::tip NOTE
+Available only when **Hierarchy** is selected.
+:::
+
+When enabled, chunks include only their heading path and content; content immediately following a parent heading is kept as a separate chunk.
+
+#### Set first chunk as global context
+
+:::tip NOTE
+Available only when **Hierarchy** is selected.
+:::
+
+Treats the first split as a global heading to maintain consistent context across the document hierarchy. Ideal for resumes where the first section identifies the subject.
+
+#### H3
 
 Specifies the heading level to define chunk boundaries: 
 
@@ -31,8 +54,9 @@ Specifies the heading level to define chunk boundaries:
 - H2
 - H3 (Default)
 - H4
+- H5
 
-Click **+ Add** to add heading levels here or update the corresponding **Regular Expressions** fields for custom heading patterns.
+Click **+ Add regular expressions** to add heading levels here or update the corresponding **Regular Expressions** fields for custom heading patterns.
 
 ### Output